Nitrogen, Aldicarb, and Cover Crop Effects on Cotton Yield and Fiber Properties

ducted with modern cotton cultivars (Touchton et al., 1984; Bauer et al., 1993; Daniel et al., 1999; Larson et Thrips, primarily Frankliniella spp., can damage cotton (Gossypal., 2001). Grass cover crop residues generally have a ium hirsutum L.) seedlings. The objectives of this study were to determine the effect of winter cover crops on thrips populations in high C/N ratio, which causes N immobilization and the cotton and to assess the yield and fiber quality response to cover need for higher N fertilizer rates than when no cover crops and N fertilizer rate with and without thrips protection. A field crop is used (Reeves, 1994). experiment was conducted on a Bonneau loamy sand soil (loamy, The economic damage caused by thrips to cotton is siliceous, thermic, Arenic Paleudult) from 1996 through 1998. Treatsubstantial. Hardee and Burris (2002) reported that ments were cover crops, N fertilizer rate, and aldicarb rate. Cover early-season thrips were the third most serious arthrocrops were rye (Secale cereale L.), crimson clover (Trifolium incarnapod pest of the U.S. cotton crop in 2001, reducing the tum L.), a clover rye mixture, and winter fallow. Nitrogen levels yield of the U.S. crop by 0.795%. Thrips are phytophawere 0, 78, and 112 kg N ha 1. Aldicarb levels were 0 and 1.18 kg a.i. gous insects with piercing mouthparts. The damage they ha 1. Aldicarb reduced thrips populations. For plots without aldicarb, cause is especially severe on seedling cotton. Depending differences among winter covers occurred at one sampling time in 1998 when fallow had more thrips than the other three winter covers. on the growing season and the degree of damage, cotton Aldicarb increased yield by 9% in 1996, 48% in 1997, and 35% in plants can often overcome this early-season stress. In 1998. In 1997 and 1998, yield increases with aldicarb were greater in areas with long growing seasons, damage does not althe winter cover and N treatment combinations that provided higher ways reduce yield (Sadras and Wilson, 1998; Terry, total N to the crop. The 0 kg N ha 1 rate tended to have lower 1992). In areas with relatively short growing seasons, yield, fiber length, length uniformity, fiber strength, micronaire, and where stand and yield losses can be substantial, prevenHunter’s b than the other two N rates. Aldicarb generally increased tative in-furrow applications of aldicarb {2-methyl-2the value of these fiber properties each year. Including agronomic (methylthio)propanal O-[(methylamino)carbonyl]oxime} practices in assessing control measures may improve integrated pest are commonly used to control thrips (All et al., 1995). management strategies for thrips in conservation tillage systems. Also, Terry (1992) found that fiber quality, a substantial component of the economic returns to growers, was not greatly affected by thrips damage. Additional informaC tillage systems are being widely tion on cropping system combinations that affect thrips used by growers for cotton production throughout populations may help improve IPM measures for this the southeastern USA. According to the 2002 National pest. Crop Residue Management Survey, acres of cotton Our hypothesis was that the attractiveness of cotton grown with no-tillage in this region have increased by seedlings to thrips would be influenced by winter cover 750% over the last 10 yr, and the southeast region has treatment, and this would influence the yield and quality 85% of the cotton grown without tillage in the USA response of cotton to aldicarb application. The objec(http://www.ctic.purdue.edu/Core4/CT/ctsurvey/2002/ tives of this study were to determine the effect of winter RegionalSynopses.html; verified 17 Nov. 2003). Consercover crops on thrips populations in cotton seedlings vation tillage systems provide a more diverse habitat and to assess how thrips protection influenced the yield for insects than conventional tillage production systems. and fiber quality response of cotton to cover crops and All et al. (1992) found fewer tobacco thrips (FrankN fertilizer rate. liniella fusca Hinds) in no-tillage than in a conventional system with surface tillage and concluded that use of noMATERIALS AND METHODS tillage may enhance integrated pest management (IPM) control of that pest. This 3-yr study was conducted at Clemson University’s Pee Dee Research and Education Center near Florence, SC, in a Cover crops can improve yield in conservation tillage field with a soil type consisting primarily of Bonneau loamy cropping systems for cotton (Bauer and Busscher, 1996; sand. The same plots were used each year, and there was no Raper et al., 2000). Both legume and nonlegume cover re-randomization of treatments between years. Treatments crops affect N fertilizer management. The value of leconsisted of winter cover (rye, crimson clover, clover rye gumes as a source of N for subsequent crops has been mixture, and fallow), N rate (0, 78, and 112 kg N ha ), and well documented (Hoyt and Hargrove, 1986; Reeves, aldicarb (0 and 1.18 kg a.i. ha ). Experimental design was 1994), and substantial work in this area has been consplit-split plot with winter cover as main plots, N rates as subplots, and aldicarb rates as sub-subplots. Sub-subplot size P.J. Bauer, USDA-ARS, Coastal Plains Soil, Water, and Plant Res. was four cotton rows that were 1-m wide and 15.2 m long. Cent., 2611 W. Lucas St., Florence, SC 29501-1242; and M.E. Roof, The experiment had four replicates each year. Clemson Univ., Pee Dee Res. and Educ. Cent., Florence, SC 29506Before beginning the experiment in 1995, all plots were 9706. Received 23 Sept. 2002. *Corresponding author (bauer@florence. chisel-plowed and disked on 3 Oct. 1995. Thereafter, the only ars.usda.gov). tillage in the experiment was the use of in-row subsoiling Published in Agron. J. 96:369–376 (2004).  American Society of Agronomy 677 S. Segoe Rd., Madison, WI 53711 USA Abbreviations: IPM, integrated pest management.